In a medium bowl combine the all purpose-flour, espresso powder (if using), baking power, baking soda and salt. Stir with a whisk and set aside.
In the bowl of your mixer, add the cocoa powder, brown sugar and vegetable oil, blend until well combined.
Add the eggs, one at a time, mixing after each addition.
Add the vanilla extract and blend.
Slowly add the dry ingredients to the chocolate mixture and mix until well blended, being careful not to to overmix the batter.
Cover the bowl with cling film and refrigerate for 4 hours or more. If pressed for time, place covered bowl in the freezer and freeze for approximately an hour and a half.
When ready to roll the cookies, place a rack in the center of your oven and preheat oven to 350ºF.
Line two baking sheets with parchment paper.
Using a cookie scoop or a tablespoon, scoop a ball of dough out, roll it in your hands and then roll the ball into the granulated sugar before rolling it a second time in powdered sugar.
Place balls of cookie dough about two inches apart on the baking sheet and repeat process until the sheet is full.
Bake in the oven for approximately 10 to 12 minutes. The cookies will look uncooked between the cracks but that is ok, they will set as they cool on the baking sheet. Please see note for explanation on determining time needed for baking cookies.
1. If dough sticks to your hands when rolling, just powder your hands with the icing sugar, the dough shouldn't stick anymore. 2. If dough is still too sticky then you should return it to the freezer or fridge for additional chilling time. 3. At 10 minutes you should have cookies that are still very fudgy inside. If you prefer them more done, leave them in the oven for an extra minute. I found that the cookies I left in for 12 minutes kept a perfectly domed shaped. Those at 10 min sunk in just slightly in the middle. I recommend baking a few on a tray to see how you like them and what the perfect time is for you before baking the entire batch of cookies.